Blood test
Clotting Screen
A clotting screen checks how well your blood forms clots, using tests such as PT and APTT to look for bleeding or clotting problems.
Quick answer
Clotting Screen: what it is and what the results mean
A clotting (coagulation) screen is a group of blood tests — typically the prothrombin time (PT/INR), activated partial thromboplastin time (APTT) and fibrinogen — that measure the different steps involved in forming a blood clot.
- Why it is done: It is used to investigate unusual bleeding or bruising, to assess clotting before surgery or procedures, to check liver function and vitamin K status, and to monitor or investigate the effect of blood-thinning medicines.
- Understanding results: Prolonged times can indicate a clotting factor deficiency, liver disease, vitamin K deficiency or the effect of anticoagulants.
What it is
A clotting (coagulation) screen is a group of blood tests — typically the prothrombin time (PT/INR), activated partial thromboplastin time (APTT) and fibrinogen — that measure the different steps involved in forming a blood clot.
Why it is done
It is used to investigate unusual bleeding or bruising, to assess clotting before surgery or procedures, to check liver function and vitamin K status, and to monitor or investigate the effect of blood-thinning medicines.
What to expect
It is an ordinary blood test from a vein in the arm, needing no special preparation. Several results are reported together.
Understanding the results
Prolonged times can indicate a clotting factor deficiency, liver disease, vitamin K deficiency or the effect of anticoagulants. The pattern of which tests are abnormal helps pinpoint the cause, guiding further tests or treatment.
Good to know
Risks and limitations
It is a safe blood test. It screens the main clotting pathways but does not detect every clotting or platelet disorder, so specialised tests may be needed for specific conditions.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Clotting Screen: frequently asked questions
What is the difference between PT and APTT?
PT (reported as INR) and APTT measure different parts of the clotting process. Which one is prolonged helps doctors work out where the problem lies, such as a specific factor deficiency or a medicine effect.
Why is a clotting screen done before surgery?
It helps ensure your blood clots normally so that bleeding can be controlled during and after the procedure, and it flags any need for precautions or treatment beforehand.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- British Society for Haematology / relevant professional body
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